Semiconductor device having heat radiating configuration

ABSTRACT

A semiconductor device and a method of manufacturing the same are disclosed. The semiconductor device includes: a casing, a board and a semiconductor chip. The chip includes: an element part; a heat sink bonded to the element part; an insulting layer located on the heat sink so that the heat sink is located between the element part and the insulating layer; and a side wall insulating layer covering all of end faces of the heat sink. The semiconductor chip is located between the casing and the board, so that the insulating layer is directed to the casing to enable heat radiation from the heat sink toward the casing via the insulating layer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No. 12/379,500 filed on Feb. 24, 2009, which is based on and claims priority to Japanese Patent Applications No. 2008-57480 filed on Mar. 7, 2008 and No. 2008-288656 filed on Nov. 11, 2008, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having a configuration for heat radiation from a semiconductor chip to a casing. The present invention also relates to a method for manufacturing such a semiconductor device.

2. Description of Related Art

There is known a semiconductor device that has a face-down mounting structure. In a typical face-down mounting structure, an electrode is located on one surface of a semiconductor chip, and is electrically connected to a wiring pattern of a board with the one surface of the semiconductor chip being directed to the board. For improvement of heat radiation efficiency from a semiconductor chip having a face-down mounting structure, a heat sink made of metal or the like is connected to another surface of the semiconductor chip, wherein the another surface is opposite to the one surface where the electrode is located (cf. U.S. Pat. No. 6,873,043).

Discussion is presented below on the above semiconductor device, as a related art. Heat radiation efficiency may improve by contacting a heat sink with a semiconductor chip or a casing that receives a board. However, since the heat sink and the casing are typically made of metal, the contact between the casing and the heat sink leads to a state where the heat sink and the casing are electrically connected. In such a case, there may generate a leak between a back side of the semiconductor chip and the casing. It is thus necessary to place an insulating layer between the heat sink and the casing to prevent the direct contacting. For example, an insulating layer may be formed on a portion of the casing that is supposed to face the heat sink. Alternatively, an insulating film may be placed between the casing and the heat sink when the semiconductor chip and the heat sink are fixed to the casing. However, when the insulating layer is formed on the casing, it is required to form insulating layers on all casings one by one. Thus, a process of forming the insulating layer becomes complicated. When an insulating film is placed between the heat sink and the casing, it is required to place the insulating film every time when the semiconductor chip and the heat sink are fixed to the casing, which results in a complicated process.

SUMMARY OF THE INVENTION

In view of the above and other points, it is an objective of the present invention to provide a semiconductor device and a method of manufacturing a semiconductor device.

According to a first aspect of the present invention, a method for manufacturing a semiconductor device is provided. The method includes: forming an insulating layer on a first surface of a heat sink. The heat sink has a second surface opposite to the first surface. The method further includes: preparing a semiconductor wafer having first and second surfaces opposite to each other. The semiconductor wafer includes: an element part having an element; and an electrode part located on the element part to provide an electric connection to the element of the element part. The electrode part is disposed on the first surface of the semiconductor wafer. The method further includes: bonding the second surface of the heat sink to the second surface of semiconductor wafer; and forming a semiconductor chip through a cutting process. The cutting process includes: dividing the semiconductor wafer together with the heat sink and the insulating layer into chips by cutting along a scribe line. The method further includes: mounting the semiconductor chip to a board having a wiring pattern, so that the electrode part of the semiconductor chip is electrically connected to the wiring pattern of the board; and positioning the semiconductor chip and the board relative to a casing made of metal. The positioning includes: directing the insulating layer of the semiconductor chip to the casing to enable heat radiation from the heat sink toward the casing via the insulating layer.

According to the above method, it is possible to simplify a process of forming an insulating layer for insulating a heat sink and a casing from each other.

According to a second aspect of the present invention, a method for manufacturing a semiconductor device is provided. The method includes: preparing multiple discrete heat sinks each having first and second surfaces opposite to each other. Each of the discrete heat sinks has an insulating layer on the first surface of the each of the discrete heat sinks. The method further includes: preparing a semiconductor wafer having first and second surfaces opposite to each other. The semiconductor wafer has: multiple element parts each having an element; and multiple electrode parts disposed on the first surface of the semiconductor wafer. The electrode parts are respectively located on the element parts so that each of the electrode parts provides an electric connection to a corresponding one of the element parts. The method further includes bonding the discrete heat sinks to the semiconductor wafer, so that: the second surface of the each of the discrete heat sinks is bonded to the second surface of the semiconductor wafer; and the discrete heat sinks are respectively located on places that correspond to the element parts. The method further includes: forming a semiconductor chip through a cutting process. The cutting process includes: dividing into chips the semiconductor wafer to which the discrete heat sinks are bonded, by cutting along a scribe line, so that each chip has a corresponding one of the discrete heat sinks and a corresponding one of the element parts. The method further includes: mounting the semiconductor chip to a board having a wiring pattern, so that the electrode part of the semiconductor chip is electrically connected to the wiring pattern of the board; and positioning the semiconductor chip and the board relative to a casing made of metal. The positioning includes: directing the insulating layer of the semiconductor chip to the casing to enable heat radiation from the heat sink toward the casing via the insulating layer.

According to the above method, it is possible to simplify a process of forming an insulating layer for insulating a heat sink and a casing from each other.

According to a third aspect of the present invention, a method for manufacturing a semiconductor device is provided. The method includes: preparing multiple discrete heat sinks each having first and second surfaces opposite to each other; preparing a semiconductor wafer having first and second surfaces opposite to each other. The semiconductor wafer has: multiple element parts each having an element; and multiple electrode parts disposed on the first surface of the semiconductor wafer. The electrode parts are respectively located on the element parts so that each of the electrode parts provides an electric connection to a corresponding one of the element parts. The method further includes: bonding the discrete heat sinks to the semiconductor wafer so that: the second surface of the each of the discrete heat sinks is bonded to the second surface of the semiconductor wafer; and the discrete heat sinks are respectively located on places that correspond to the element parts. The method further includes: filling a gap between the discrete heat sinks with an insulating material and forming an insulating layer on the first surface of each of the discrete heat sink; and forming a semiconductor chip through a cutting process. The cutting process includes cut, along a scribe line, of the insulating material together with the semiconductor wafer to which the discrete heat sinks are bonded, so that: chips are provided by dividing; each chip has a corresponding one of the discrete heat sinks and a corresponding one of the element parts; and the each chip has a side-wall insulating film that is made of the insulating material and that covers an end face of the heat sink. The method further includes: mounting the semiconductor chip to a board having a wiring pattern, so that the electrode part of the semiconductor chip is electrically connected to the wiring pattern of the board; and positioning the semiconductor chip and the board relative to a casing made of metal. The positioning includes: directing the insulating layer of the semiconductor chip to the casing to enable heat radiation from the heat sink toward the casing via the insulating layer.

According to the above method, it is possible to simplify a process of forming an insulating layer for insulating a heat sink and a casing from each other.

According to a fourth aspect of the present invention, a method for manufacturing a semiconductor device is provided. The method includes: preparing multiple discrete heat sinks each having first and second surfaces opposite to each other. Each of the discrete heat sinks has an insulating layer on the first surface the each of the discrete heat sinks. The method further includes: preparing a semiconductor wafer having first and second surfaces opposite to each other. The semiconductor wafer has: multiple element parts each having an element; and multiple electrode parts respectively located on the element parts. The electrode parts are disposed on the first surface of the semiconductor wafer, so that each of the electrode parts provides an electrical connection to the element of a corresponding one of the element parts. The method further includes: bonding the discrete heat sinks to the semiconductor wafer so that: the second surface of the each of the discrete heat sinks is bonded to the second surface of the semiconductor wafer; and the discrete heat sinks are respectively located on places that correspond to the element parts. The method further includes: bonding a support member to the first surface of the semiconductor wafer; dividing into portions the semiconductor wafer to which the discrete heat sinks are bonded, so that the divided portions respectively have the element parts; filling with an insulating material a gap between the discrete heat sinks and a gap between the element parts; and forming a semiconductor chip through a cutting process. The cutting process includes: cutting the insulating material along a scribe line to provide chips by dividing, so that the semiconductor chip has a side-wall insulating film that is made of the insulating material and that covers an end face of the heat sink and an end face of the element part. The method further includes: mounting the semiconductor chip to a board having a wiring pattern, so that the electrode part of the semiconductor chip is electrically connected to the wiring pattern of the board; and positioning the semiconductor chip and the board relative to a casing made of metal. The positioning includes: directing the insulating layer of the semiconductor chip to the casing to enable heat radiation from the heat sink toward the casing via the insulating layer.

According to the above method, it is possible to simplify a process of forming an insulating layer for insulating a heat sink and a casing from each other.

According to a fifth aspect of the present invention, a method for manufacturing a semiconductor device is provided. The method includes: forming an insulating layer on a first surface of a heat sink. The heat sink has a second surface opposite to the first surface. The method further includes: preparing a semiconductor wafer having first and second surfaces opposite to each other. The semiconductor wafer includes: an element part having an element; and an electrode part located on the element part to provide an electric connection to the element of the element part. The electrode part is disposed on the first surface of the semiconductor wafer. The method further includes: bonding the second surface of the heat sink to the second surface of semiconductor wafer; and forming a semiconductor chip through a cutting process. The cutting process includes: dividing the semiconductor wafer together with the heat sink and the insulating layer into chips by cutting along a scribe line.

According to the above method, it is possible to simplify a process of forming an insulating layer for insulating a heat sink and a casing from each other.

According to a sixth aspect of the present invention, a semiconductor device is provided. The semiconductor device includes: a casing made of metal; a board having a wiring pattern; and a semiconductor chip. The semiconductor chip includes: an element part located in a semiconductor substrate, having an element, and having first and second surface opposite to each other; an electrode part located on the first surface of the element part to provide an electrical connection to the element of the element part; a heat sink bonded to the second surface of the element part; a insulting layer located on the heat sink so that the heat sink is located between the element part and the insulating layer; and a side wall insulating layer covering all of end faces of the heat sink. The semiconductor chip is located between the casing and the board, so that the electrode part of the semiconductor chip is electrically connected with the wiring pattern of the board, and so that heat from the heat sink is radiated toward the casing via the insulating layer.

According to the above semiconductor device, it is possible to ensure insulation from the semiconductor chip from the casing.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a cross sectional diagram illustrating a semiconductor device in accordance with a first embodiment;

FIGS. 2A to 2D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with a first embodiment;

FIG. 2E is a perspective view that corresponds to FIG. 2A;

FIG. 2F is a perspective view that corresponds to FIG. 2C;

FIG. 3 is a cross sectional diagram illustrating a MOSFET that a manufacturing method according to a first embodiment is applicable to;

FIG. 4 is a cross sectional diagram illustrating a semiconductor device in accordance with a second embodiment;

FIG. 5 is a layout diagram illustrating an upper side of a semiconductor device that corresponds to that in FIG. 4;

FIGS. 6A to 6D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device exemplified in FIG. 4;

FIG. 7 is a layout diagram illustrating an upper side of a semiconductor device in a process of fling a ditch with an insulating material;

FIGS. 8A to 8D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with a third embodiment;

FIG. 9 is a cross sectional diagram illustrating a semiconductor device in accordance with a fourth embodiment;

FIGS. 10A to 10C are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with a fifth embodiment;

FIG. 11 is a top view that corresponds to FIG. 10A

FIGS. 12A to 12E are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with a sixth embodiment;

FIGS. 13A to 13C are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with a seventh embodiment;

FIGS. 14A to 14D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with an eighth embodiment;

FIGS. 15A to 15D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with a ninth embodiment;

FIG. 16 is a top view illustrating a layout of a scribe line and an element isolation trench;

FIGS. 17A to 17D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with a tenth embodiment;

FIG. 18 is a cross sectional diagram illustrating a semiconductor element in accordance with a modification example; and

FIG. 19 is a cross sectional diagram illustrating semiconductor chip in accordance with another modification example.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Exemplary embodiments are described below with reference to the accompanying drawings. In the followings, like parts refer to like reference numerals.

First Embodiment

A first embodiment is described below. FIG. 1 is a cross sectional diagram illustrating a semiconductor device 1 in accordance with a first embodiment.

The semiconductor device 1 includes parts illustrated in, for example, FIG. 1 as a portion of the semiconductor device 1. The semiconductor device 1 may correspond to, for example, a power package having a power device, a central processing unit (CPU) generating a large amount of heat, or a passive device generating a large amount of heat. Alternatively, the semiconductor device 1 may correspond to a power unit having an element in addition to the above power package. Alternatively, the semiconductor device 1 may correspond to an electronic control unit (ECU) having a circuit or the like in addition to the above power package.

As shown in FIG. 1, the semiconductor device 1 includes a semiconductor chip 2, a board 3 (i.e., a printed circuit board) and a casing 4.

The semiconductor chip 2 includes an element part 2 a, an electrode part 2 b, a heat sink 2 c and an insulating layer 2 d. The element part 2 a is formed through dividing into chips a semiconductor substrate in which semiconductor elements are formed. The electrode part 2 b is formed on a front surface side of the element part 2 a. The heat sink 2 c is bonded to a rear surface side of the element part 2 a. The insulating layer 2 d is formed on a front surface of the heat sink 2 c.

The element part 2 a includes a semiconductor element such as a MOSFET, IGBT or the like. The semiconductor element includes impurity regions. One or more of the impurity regions is electrically connected with the electrode part 2 b. The electrode part 2 b includes, for instance, a conductive bump made of solder. The heat sink 2 c includes a metal plate made of, for example, copper. The heat sink 2 c can be used for heat radiation from the element part 2 a. More specifically, the semiconductor device 1 is configured such that the heat generated in the element part 2 a is radiated through heat conduction to the casing 4 via the heat sink 2 c. The heat sink 2 c and the casing 4 can be made of metal when heat radiation performance is took into account. If the heat sink 2 c and the casing 4 made of metal merely contact with each other, the heat sink 2 c and the casing 4 are electrically connected with each other. To insulate the heat sink 2 c and the casing 4 from each other, the insulating layer 2 d is disposed on the front surface of the heat sink 2 c. The insulating layer 2 d may be made of a material having a high thermal conductivity of, for example, 10 W/mK or more, and may have a film shape having a thickness of, for example, 100 μm.

The board 3 is, for example, a printed circuit board, a ceramic board, or the like. The board 3 has a wiring pattern. The semiconductor chip is disposed face-down on the board 3 and the electrode part 2 b of the element part 2 a is electrically connected to a predetermined part of the wiring pattern of the board 3. Thereby, the semiconductor element can be connected to or mounted to an electric circuit inside the casing 4.

The casing 4 receives the element part 2 a and the board 3. The casing 4 is made of metal to improve heat radiation performance, as described above. The casing 4 may further receive another element (not shown) mounted to the board 3.

The semiconductor device 1 according to the present embodiment has the above configuration. A method of manufacturing such a semiconductor device 1 is described below.

FIGS. 2A to 2D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device in accordance with the present embodiment. FIG. 2E is a perspective view that corresponds to FIG. 2A. FIG. 2F is a perspective view that corresponds to FIG. 2C.

In a process exemplified in FIG. 2A, a metal plate for use in forming the heat sink 2 c is prepared. In addition, an insulating film made of an insulating material is prepared. Then, as shown in FIG. 2B, the insulating film is bonded to a first surface of the metal plate by thermo compression bonding to integrate together. Thereby, a heat sink 2 c having an insulating layer 2 d on the first surface is formed.

In a process exemplified in FIG. 2C, a single semiconductor wafer is prepared. Through a semiconductor process technology, a semiconductor element and an electrode part 2 b is formed in the semiconductor wafer, so that the electrode part 2 b is located on a first surface side of the semiconductor wafer. Then, the heat sink 2 c having an insulating layer is arranged relative to the semiconductor wafer such that a side of the heat sink 2 c (i.e., a second surface side) opposite to the insulating layer side faces a side of the semiconductor wafer (a second surface side) opposite to an electrode part side. Then, in a process exemplified in FIG. 2D, the heat sink 2 c having the insulating layer is bonded to the semiconductor wafer by using, for example, an adhesive agent. In the above case, a shape of the metal plate or the insulating layer 2 d may be different from that of the semiconductor wafer. Alternatively, a shape of the metal plate or the insulating layer may be similar to that of the semiconductor wafer. For example, a shape having an orientation flat may be employed, which shape may be circular with a part being cut. When the orientation flat is provided, it is possible to perform subsequent processes by using a semiconductor process technology. For example, it is possible to perform subsequent processes with various apparatuses for a semiconductor process technology. The bonding of the heat sink 2 c to the semiconductor wafer may made by direct wafer bonding without using an adhesive agent.

Then, the semiconductor wafer together with the insulating layer 2 d and the heat sink 2 c are diced into chips. Through the above manners, a semiconductor chip 2 as exemplified in FIG. 1 is manufactured that includes the element part 2 a, the electrode part 2 b, the heat sink 2 c and the insulating layer 2 d. Since the semiconductor chip 2 is manufactured through the above manners, the element part 2 a, the heat sink 2 c and the insulating layer 2 d have end faces (i.e., side surfaces) produces by the dicing cut, and the end faces are generally in a same plane.

The semiconductor chip 2 is placed face-down, bonded and mounded to the board 3 by using, for example, flip chip or solder. Then, the semiconductor chip 2 and the board 3 are accommodated in the casing 4. Through the above manners, the semiconductor device 1 as exemplified in FIG. 1 is manufactured.

According to the present embodiment, as described above, it is possible to manufacture multiple semiconductor chips 2 at one time through: bonding a heat sink 2 c and an insulating layer 2 d to a semiconductor wafer that is in the form of wafer and that a semiconductor element is formed in; and dicing or cutting the semiconductor wafer together with the heat sink 2 c and the insulating layer 2 d. Therefore, the semiconductor chip 2 has already included the insulating layer 2 d in manufacturing a semiconductor device 1 having a configuration for heat radiation from a heat sink 2 c to a casing 4 via an insulating layer 2 d. Thus, it becomes possible to simplify a process of forming an insulating film for insulation between the heat sink 2 c and the casing 4, compared to a case where it is necessary to place an insulating film every time when a heat sink 2 c bonded to an element part 2 a is fixed to the casing 4. Further, the semiconductor device 1 is configured such that the insulating layer 2 d is directly formed on the semiconductor chip 2. Thus, the insulating layer 2 d needs not to be large, compared to a case where it is necessary to bond an insulating layer to a semiconductor chip in a later process. Consequently, it is possible to downsize the semiconductor device.

The above manufacturing method is applicable to almost any types of semiconductor devices 1 having a structure for heat radiation. In particular, the above manufacturing method may be usefully applied to a semiconductor device having a power device generating a large amount of heat or a device with non-negligible switching loss. Such a power device is for example a MOSFET, an IGBT or the like. The device with non-negligible switching loss is for example a high-frequency switching device.

It may be suitable to apply the above manufacturing method to fabrication of a MOSFET having a sectional configuration as exemplified in FIG. 3.

As shown in FIG. 1, the element part 2 a is located on an electrode part 2 b side of the semiconductor chip 2. The element part 2 a can have a configuration described as follows. As shown in FIG. 3, an n− type drift layer 22 is formed in a surface portion of an n+ type substrate 21. A p type base region 23 is formed in a surface portion of the n+ type substrate 21. A n+ type source region 24 is formed so as to terminate inside the p type base region 23. A gate insulating film 25 is formed on a surface of the element part 2 a. A gate electrode 26 is formed so that, through the gate insulating film 25, the gate electrode 26 faces a part of a surface of the p type base region 23, which part of the surface of the p type base region 23 is located between the n− type drift layer 22 and the n+ type source region 24.

Further, an interlayer insulating film 27 is formed so as to cover the gate electrode 26. A source electrode 28 is formed so as to cover the interlayer insulating film 27. Through a contact hole formed in the insulating film 27, the source electrode 28 is electrically connected with the n+ type source region 24 and the p type base region 23. The n+ type substrate 21 includes a n+ type contact region 21 a as a part of the n+ type substrate 21, which may correspond to a remaindered region where the n− type drift layer 22 is not formed. A drain electrode 29 is formed on a surface of the n+ type contact region 21 a.

When a semiconductor device includes a MOSFET as exemplified in FIG. 3, the above-described electrode part 2 b is connected to a source electrode 28 or a drain electrode 29.

The MOSFET can have the above configuration. In such MOSFETs, application of a gate voltage to the gate electrode 26 controls formation of a channel in a surface portion of the base region 23. The channel can allow electrical conduction between the n+ type source region 24 and the n− type drift layer 22 for source-drain current flow. In the above case, an electronic current from the n− type drift layer 22 into the n+ type substrate 21 reaches to a drain electrode 29 via the n+ type contact region 21 a. The above-described manufacturing method is applicable to a MOSFET having the above configuration.

Second Embodiment

In a first embodiment, the heat sink 2 c is exposed from an end face of the semiconductor chip 2. When working voltages of a semiconductor element are less than or equal to 60 V for instance, a configuration of a first embodiment can sufficiently ensure insulation of the heat sink 2 c or the element part 2 a from the casing 4 by means of grounding the casing 4 or the like. However, since the heat sink 2 c is conductor, when a semiconductor element in the semiconductor chip 2 operates at high voltages, the presence of a thin insulating layer 2 d only is difficult to ensure the insulation of the heat sink 2 c or the element part 2 a from the casing 4. Taking into account semiconductor devices used in high voltages, the present embodiment presents a configuration for enhancing the insulation of the heat sink 2 c or the element part 2 a from the casing 4.

FIG. 4 is a cross sectional diagram illustrating a semiconductor device 1 in accordance with the present embodiment. FIG. 5 is a layout diagram illustrating an upper side of a semiconductor device 1. A difference between a first embodiment and a second embodiment includes a configuration for insulation between a heat sink 2 c and a casing 4.

In the present embodiment, as shown in FIG. 4, the semiconductor chip 2 for the semiconductor device 1 includes the side-wall insulating film 2 e on the end surface of a heat sink 2 c. More specifically, the semiconductor chip 2 has a ditch 2 f and the side-wall insulating film 2 e in the ditch 2 f. The ditch 2 f is formed by partially removing the heat sink 2 c and the element part 2 a from a front surface side of the heat sink 2 c. As shown in FIG. 5, the side-wall insulating film 2 e is formed so as to wholly surround a periphery of the semiconductor chip 2. In the periphery, the side-wall insulating film 2 e covers the end faces of the heat sink 2 c. Accordingly, the end faces of the heat sink 2 c are not exposed to an outside. In addition, a distance between an end face of the semiconductor chip 2 and the casing is made longer. The above configuration can enhance the insulation of the heat sink 2 c or the element part 2 a from the casing 4 in the end faces of the semiconductor chip 2.

A method of manufacturing the above semiconductor device 1 is described below in accordance with the present embodiment.

FIGS. 6A to D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device 1 in accordance with the present embodiment. Manufacturing processes of a semiconductor chip 2 of the present embodiment are generally similar to those of the first embodiment. Differences include those as shown in FIGS. 6A to 6D.

In a process exemplified in FIG. 6A, the processes exemplified in FIGS. 2A to 2D according to the first embodiment are performed. That is, a structure is formed in which a heat sink 2 c and an insulating layer 2 d are located on a rear surface side of a semiconductor wafer that a semiconductor element is formed in. Then, in a process exemplified in FIG. 6B, a ditch 2 f is formed from the insulating layer 2 d along a scribe line 5 (see FIG. 7). A depth of the ditch 2 f is such that the semiconductor wafer is not cut into chips. More specifically, the ditch 2 f penetrates the insulating layer 2 d and the heat sink 2 c, and has a bottom inside the semiconductor wafer. A width of the ditch 2 f is set wider than a kerf width that is to be produced in a cutting process performed later. For example, a mask (not shown) is placed on the insulating layer 2 d, and then, the ditch 2 f is formed by, for example, etching or operating a dicing saw along the scribe line 5 from above the insulating layer 2 d.

In the forming of the ditch 2 f, a mark for alignment may be required. When, as described above, the insulating layer 2 d and the heat sink 2 c has a generally same shape as the semiconductor wafer, it is possible to precisely form the ditch 2 f at a desired position since the orientation flat can be used as the mark for alignment. Alternatively, a mark for alignment may be preliminary formed in the heat sink 2 c or the insulating layer 2 d, and the heat sink 2 c and the insulating layer 2 d may be bonded to the semiconductor wafer by using the mark for alignment for positioning. In such a case, it is possible to form the ditch 2 f while the mark for alignment is being identified from an insulating layer 2 d side.

In a process exemplified in FIG. 6C, the ditch 2 f is filled with an insulating material. For example, the ditch 2 f is filled by spin coating a resin material or by depositing an insulating layer made of, for example, silicon oxide. The deposition of an insulating layer may be performed by chemical vapor deposition (CVD) at low temperatures. FIG. 7 is a layout diagram illustrating an upper side of a semiconductor device in a process of fling a ditch with an insulating material. As shown in FIG. 7, a width of the ditch 2 f is wider than that of the scribe line 5, and the insulating material is embedded in the ditch 2 f. The scribe line 5 is located along a center of the ditch 2 f.

After the above processes, a cutting process is performed, as exemplified in the FIG. 6D. Dicing cutting along the scribe line 5 is carried out by using, for example, a dicing saw whose cutting width is smaller than the width of the ditch 2 f. Thereby, the semiconductor wafer together with the insulating layer 2 d and the heat sink 2 c are divided into chips. Through the above process, the semiconductor chip 2 exemplified in FIG. 4 is manufactured, the semiconductor chip 2 having an element part 2 a, an electrode part 2 b, a heat sink 2 c, an insulating layer 2 d, and a side-wall insulating layer 2 e that covers an end surface of the heat sink 2 c.

In the above example, the cutting process is performed using a dicing saw. Alternatively, the cutting process can be carried using various techniques. For example, the cutting process may performed by etching, laser cutting, or the like. In the following embodiments, a cutting process by using a dicing saw will be explained as an example. However, in the following embodiments also, the cutting process can be performed using another technique.

The semiconductor device 1 of the present embodiment includes advantages that the semiconductor device 1 of the first embodiment have. In addition, according to the present embodiment, it is possible to enhance the insulation of the heat sink 2 c or the element part 2 a from the casing 4 in the end faces of the semiconductor chip 2, since the semiconductor chip 2 includes the side-wall insulating film 2 e.

Third Embodiment

In the present embodiment, a method is presented below for manufacturing a configuration for insulation of the heat sink 2 c or the element part 2 a from the casing 4.

FIGS. 8A to 8D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor chip 2 for a semiconductor device 1. Manufacturing processes of a semiconductor chip 2 of the present embodiment are generally similar to those of the first embodiment. Difference includes those shown in FIGS. 8A to 8D.

In a process exemplified in FIG. 8A, the processes exemplified in FIGS. 2A to 2D according to the first embodiment are performed. That is, a structure is formed in which a heat sink 2 c and an insulating layer 2 d are located on a rear surface side of a semiconductor wafer that a semiconductor element has been formed in. Then, a support member 6 is bonded to the electrode part 2 b and the front surface of the semiconductor wafer, so that the semiconductor wafer, the heat sink 2 c and the insulating layer 2 d are fixed. A ditch 2 f is formed along the scribe line 5 from an insulating layer 2 d side, so the semiconductor wafer together with the heat sink 2 c and the insulating layer 2 d are divided into portions for respective chips. The depth of the ditch 2 f reaches to the support member 6 but is not so deep as to divide the support member 6 into pieces. In the above case, since the support member 6 is not divided, when the semiconductor wafer, the heat sink 2 c and the insulating layer 2 d are divided, the support member 6 supports the divided ones in an integral manner. For the above dividing, a process exemplified in FIG. 6B in the second embodiment can be employed.

Then, in a process exemplified in FIG. 8B, the ditch 2 f that provides the divided portions for respective chips is filled with an insulating material in a manner similar to that exemplified in FIG. 6C. Then, in a process exemplified in FIG. 8C, dicing cut is performed along the scribe line 5 by using a dicing saw whose kerf width is smaller than the width of the ditch 2 f, in a manner similar to that exemplified in FIG. 6D. Thereby, it is possible to provide a semiconductor chip 2 whose end surfaces are entirely covered by a side-wall insulating film 2 e. In the above manners, the dicing cut is performed so that a depth reaches to the support member 6 but does not divide the support member 6. Thus, when the semiconductor wafer, the heat sink 2 c and the insulating layer 2 d are divided, the support member 6 supports the divided ones in an integral manner. In a process exampled in FIG. 8D, the support member 6 is removed from the semiconductor chips 2. Thereby, it is possible to provide the semiconductor chip 2 having a configuration substantially identical to that of the second embodiment. Then, using the semiconductor chip 2 manufactured through the above manners, it is possible to manufacture a semiconductor device 1 similar to that of the second embodiment.

Fourth Embodiment

The present embodiment employs a semiconductor chip 2 that is manufactured through processes of a third embodiment. There will be described below a configuration and manufacturing method of a semiconductor device 1 that can further enhance the insulation of the heat sink 2 c or the element part 2 a from the casing 4.

FIG. 9 is a cross sectional diagram illustrating a semiconductor device 1 in accordance with the present embodiment. As shown in FIG. 9, the semiconductor device 1 includes a board 3 and a semiconductor chip 2 formed by a manufacturing method of a third embodiment. That is, end faces of the semiconductor chip 2 are entirely covered by the side-wall insulating film 2 e. The board 3 and the semiconductor chip 2 are electrically connected with each other. The semiconductor device 1 may further include an intermediate material 7. The intermediate material 7 is located between the element part 2 a and the board 3, and between a surface of the electrode part 2 b and the board 3. The intermediate material 7 covers a surface of the element part 2 a to isolate the covered surface from outside while the semiconductor chip 2 is being electrically connected with the board 3.

When the semiconductor chip 2 is electrically connected to the board 3, the intermediate material 7 may be placed between the element part 2 a and the board 3, and between the surface of the electrode part 2 b and the board 3. The intermediate material 7 is, for example, a non-conductive paste (NCP), a non-conductive film (NCF), an anisotropic conductive paste or the like, and ensures insulation of the front surface of the semiconductor chip 2.

Accordingly, it is possible to further enhance insulation of the heat sink 2 c or the element part 2 a from the casing 4. Further, it is possible to protect the semiconductor chip 2 and the heat sink 2 c in a harsh environment, which is for example a corrosive environment.

Fifth Embodiment

A difference between the present embodiment and the above embodiments includes the followings. In the present embodiment, discrete heat sinks 2 c for respective chips are preliminarily prepared. Through bonding the discrete heat sinks 2 c to a semiconductor wafer, a semiconductor device 1 having a configuration of the above embodiments is manufactured.

FIGS. 10A to 10C are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device 1 in accordance with the present embodiment. FIG. 11 is a plan view diagram illustrating a manufacturing process that corresponds to FIG. 10A.

As shown in FIG. 10A, element parts 2 a are formed in a semiconductor wafer. The discrete heat sinks 2 c each having an insulating layer 2 d are placed on regions that respectively correspond to element parts 2 a of the semiconductor wafer. Then, as shown in FIG. 10B, a resin member is placed on a front surface of the semiconductor wafer. Thereby, a gap between the discrete heat sinks 2 c are filled with the resin member and the side-wall insulation film 2 e is formed. Then, as shown in FIG. 10C, dicing cut is performed along a scribe line 5 by using a dicing saw whose kerf width is smaller than the gap between the discrete heat sinks 2 c. Thereby, the semiconductor wafer together with the side-wall insulating film 2 e is divided into chips. According to the above manners, a semiconductor chip 2 having a configuration similar to that exemplified in FIG. 4 is manufactured. That is, the manufactured semiconductor chip 2 includes the element part 2 a, the electrode part 2 b, the heat sink 2 c, the insulating layer 2 d, and the side wall insulating film 2 e covering the end surfaces of the heat sink 2 c.

By using the discrete heat sinks 2 c for respective chips, it is possible to manufacture a semiconductor device 1 having a configuration similar to those of the above embodiments.

Sixth Embodiment

In the present embodiment, discrete heat sinks 2 c are preliminarily prepared for respective chips in a manner similar to that of a fifth embodiment. In the present embodiment, when the discrete heat sinks 2 c are prepared, the discrete heat sinks 2 c are placed on a support member so that the discrete heat sinks 2 c are positioned at places that corresponding to respective element parts 2 a.

FIGS. 12A to 12E are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device 1 in accordance with the present embodiment. The processes performed after preparing heat sinks 2 c, which including position the discrete heat sinks 2 c at places that respectively correspond to the element parts 2 a, are generally similar to those of a fifth embodiment. A difference includes the followings.

As shown in FIG. 12A, a plate shape heat sink 2 c (i.e., a heat sink plate 2 c), a plate shape insulating layer 2 d (i.e., an insulating layer plate 2 d) and a support member 30 including an adhesive member etc. are prepared. The plated shape heat sink 2 c is one that has not divided into discrete portions yet and that has enough dimensions to contain multiple element parts 2 c. Then, as shown in FIG. 12B, the plate shape insulating layer 2 d and the support member 30 are successively bonded to the plate shape heat sink 2 c. Then, as shown in FIG. 12C, the plate shape heat sink 2 c and the plate shape insulating layer 2 d are divided into discrete portions (i.e., discrete heat sinks 2 c) for respective chips by, for example, etching. In the above process, a mask is placed on a surface of the heat sink 2 c in advance of the etching. After the dividing, the discrete heat sinks 2 c and the discrete insulating layers 2 d are supported by the support member 30 while being respectively positioned at places that correspond to element part 2 a.

Then, as shown in FIG. 12D, by using the support member 30, the discrete heat sinks 2 c each having a discrete insulating layer 2 d are bonded to the semiconductor wafer. As shown in FIG. 12E, the support member 30 is removed from the heat sinks 2 c, thereby to form a structure where the heat sink 2 c are located on the semiconductor wafer at places that respectively correspond to the element parts 2 a. After the removing, the processes generally identical to those described in FIGS. 10B and 10C are performed. Through the above manners, it is possible to manufacture a semiconductor device 1 as exemplified in FIG. 4.

According to the present embodiment, the prepared discrete heat sinks 2 c are in a state where the support member 30 supports and positions the discrete heat sinks 2 c at places that respectively correspond to element parts 2 a. Therefore, it becomes possible to position with ease the heat sinks 2 c on the semiconductor wafer.

Seventh Embodiment

In the present embodiment, discrete heat sinks 2 c for respective chips are preliminary prepared in a manner similar to that of fifth and sixth embodiments. However, a difference includes the followings: in the present embodiment, an insulating layer 2 d is formed after the discrete heat sinks 2 c are bonded to a semiconductor wafer.

FIGS. 13A to 13C are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device 1 in accordance with the present embodiment. As shown in FIG. 13A, the discrete heat sinks 2 c for respective chips are placed on the semiconductor wafer. Then, as shown in FIG. 13B, a side-wall insulating film 2 e and an insulating layer 2 d are formed at a same time. In a process exemplified in FIG. 13C, a process generally similar to that exemplified in FIG. 10C is performed. Through the above manners, it is possible to manufacture a semiconductor device as exemplified in FIG. 4.

As described above, in the present embodiment, the insulating layers 2 d are not preliminarily formed on the discrete heat sinks 2 c but formed at a same time when the side-wall insulating film 2 e is formed. That is, the insulating layers 2 d are formed after the discrete heat sinks 2 c for respective chips are placed on the semiconductor wafer. In the above example of the present embodiment, the formation of the insulating layer 2 d after the bonding of the discrete heat sinks 2 c to the semiconductor is performed in generally line with processes of a fifth embodiment.

Alternatively, the formation of the insulating layer 2 d after the bonding of the discrete heat sinks 2 c to the semiconductor can be performed in generally line with processes of a sixth embodiment. For example, the discrete heat sinks 2 c cab be prepared through: placing a heat sink plate 2 c on a support member 30; and dividing the heat sink plate 2 c into the discrete heat sinks 2 c that are supported by the support member 30. The discrete heat sinks 2 c that are supported by the support member 30 are bonded to the semiconductor wafer. Then, the support member may be removed from the discrete sinks 2 c, and the side-wall insulating film 2 e and the insulating layer 2 d may be formed at a same time.

Eighth Embodiment

The present embodiment is generally similar to fifth and sixth embodiments in that the discrete heat sinks 2 c for respective chips are preliminary prepared. A difference includes a manner where a semiconductor wafer is divided into portions for respective chips before formation of the side-wall insulating film 2 e.

FIGS. 14A to 14D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device 1 in accordance with the present embodiment. As shown in FIG. 14A, discrete heat sinks 2 c having insulating layers 2 d for respective chips are placed on a front surface of a semiconductor wafer. In addition, a support member 30 including an adhesive member etc. is bonded to a rear surface of the semiconductor wafer, which rear surface is opposite to the front surface on which the heat sink 2 c and the insulating layer 2 d are placed. Then, as shown in FIG. 14B, the semiconductor wafer is etched while utilizing the heat sink 2 c with the insulating layer 2 d as a mask, so that the semiconductor wafer is divided into portions for respective chips.

As shown in FIG. 14C, a resin member is placed on an upper surface side of the support member 30. Thereby, a gap between the discrete heat sinks 2 c and a gap between the element parts 2 a is filled with an insulating material to form the side-wall insulating film 2 e. Then, as shown in FIG. 14D, dicing cut is made along a scribe line 5 by using a dicing saw whose kerf width is smaller than the gap between the element parts 2 a and the gap between the discrete heat sinks 2 c. Thereby, the semiconductor wafer together with the side-wall insulating film 2 e is divided into portions for chips. Through the above manners, there is provided a configuration as exemplified in FIG. 4.

As described above, it is possible to form the side-wall insulating film 2 e after a semiconductor wafer is divided into portions for respective chips to provide discrete the discrete element parts 2 a in addition to the discrete heat sinks 2 c.

In the above processes, the insulating layers 2 d and the side-wall insulating film 2 e may be formed at a same time in manners similar to a seventh embodiment, instead of preparing the discrete heat sinks 2 c having the insulating layers 2 d for respective chips. That is, the insulating layers 2 d may not be located on the heat sinks 2 c before the semiconductor wafer is divided into portions for respective chips. The insulating layers 2 d may be formed on the heat sinks 2 c at a same time when the side-wall insulating film 2 e is formed, as shown in FIG. 14 c.

Ninth Embodiment

In the present embodiment, there will be described below a method of manufacturing a semiconductor device utilizing a Silicon on Insulator (SOI) substrate as a semiconductor wafer and having a configuration as exemplified in FIG. 4.

FIGS. 15A to 15D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device 1 in accordance with the present embodiment. As shown in FIG. 15A, an SOI substrate has an active layer 42, a support base 40 and a buried insulation film 41 located between the active layer 42 and the support base 40. In the use of SOI substrate, when an element isolation trench 43 formed in the active layer 42 surrounds the element parts 2 a, it becomes possible to insulate the element parts 2 a from an end face of a semiconductor chip 2. Thus, in the present embodiment, the element isolation trench 43 is formed along and on both sides of a scribe line 5 when the element parts 2 a are formed.

FIG. 16 is a top view illustrating a layout of a scribe line 5 and an element isolation trench 43. It should be noted that, although FIG. 16 is not a sectional view, a region corresponding to the element isolation trench 43 is illustrated with hatching in FIG. 16 for clarification.

As shown in FIG. 16, the element isolation trench 43 is formed along an on both sides of whole scribe line 5. Side walls of the element isolation trench structure 43 are parallel to each other. A width of the element isolation trench 43 is larger than a kerf width that is to be produced in a cutting process. Also, the width of the element isolation trench 43 is set to a dimension enough to ensure a thickness of the side-wall insulating film 2 e that is to be formed in a later process.

Then, a heat sink 2 c and an insulating layer 2 d are bonded to a rear surface side of the SOI substrate that an element part 2 a has been formed in. Then, as shown in FIG. 15B, a ditch 2 f is formed along the scribe line 5 from an insulating layer 2 d side in a manner similar to that exemplified in FIG. 6B according to a second embodiment. In the above process, the ditch 2 f is formed to reach to at least the buried insulating film 41.

As shown in FIG. 15C, a side wall insulating film 2 e is formed by filling the ditch 2 f with an insulating material. Then, as shown in FIG. 15D, the semiconductor wafer together with the side-wall insulating film 2 e are divided into chips by cutting along the scribe line 5. Thereby, a semiconductor device 1 with a configuration similar to that exemplified in FIG. 4 is manufactured by using an SOI substrate.

As described above, when an SOI substrate is employed, it is also possible to manufacture a semiconductor device 1 having a configuration similar to that exemplified in FIG. 4.

Tenth Embodiment

In the present embodiment, a ditch 2 f for providing a side-wall insulating film 2 e is formed in a manner similar to that in third and ninth embodiments. A difference includes the followings: the ditch 2 f is formed not through cutting from a heat sink 2 c side but through cutting from a semiconductor wafer side.

FIGS. 17A to 17D are cross sectional diagrams each illustrating a manufacturing process of a semiconductor device 1 in accordance with the present embodiment. As shown in FIG. 17A, a structure is formed in which heat sinks 2 c and insulating layers 2 d are placed on a rear surface side of a semiconductor wafer that semiconductor elements have been formed in. Then, a support member 6 is fixed and bonded not on a front surface side of the semiconductor wafer but on an insulating layer 2 d side. The semiconductor wafer is cut along a scribe line 5 from a semiconductor wafer side and divided into chips. Thereby, a ditch 2 f is formed so as to have a depth reaching to the support member 6 and so as to be not so deep to divide the support member 6 into pieces.

Then, as shown in FIG. 17B, the ditch 2 f is filled with an insulating material to from a side-wall insulating film 2 e. As shown in FIG. 17C, a trench 2 g is formed in a center part of the side-wall insulating film 2 e by, for example, dry etching, so that the trench 2 g has a smaller width in a deeper part, that is, the trench 2 g has side surfaces with a tapered shape. The trench 2 g has a depth deeper than the insulating layer 2 d. Then, as shown in FIG. 17D, a cutting process is performed by using, for example, a dicing saw, so that cutting of the side-wall insulating film 2 e provides chips. Through the above manners, it is possible to manufacture a semiconductor device 1 having a configuration exemplified in FIG. 4.

According to the present embodiment, the support member 6 can be removed. Alternatively, the support member 6 may not be removed and may be utilized as a part of the semiconductor chip.

As described above, it is also possible to manufacture a semiconductor device 1 having a configuration similar to that exemplified in FIG. 4, through dicing cut from the semiconductor wafer side. To form the side-wall insulating film 2 e, it may not be necessary to form the trench 2 g. However, the formation of the trench 2 g may allow the followings. When the semiconductor device 1 is one that is to be mounted to a casing (not shown) or a circuit board (not shown) in a face-up mounting manner, since the side wall of the side-wall insulating film 2 e is tapered, it is possible to depositing a conductive layer on the tapered side wall and it is possible form a wiring pattern by pattering the conductive pattern.

(Modifications)

A semiconductor device 1 according to the above embodiments can be modified in various ways. For example, although the above embodiments give examples of semiconductor devices 1 as those having sectional configurations shown in the drawings, a semiconductor device 1 can have various alternative configurations.

In the above embodiments, a heat sink 2 c is used as an element for heat radiation. Alternatively, a configuration and a method according to the above embodiments may be applied to such a semiconductor chip 2 where: a heat sink 2 c functions as a member for conducting a current in a lateral direction, which may be parallel to the front surface of the semiconductor chip 2.

FIG. 18 is a cross sectional diagram illustrating a semiconductor element where a heat sink 2 c functions as an element for conducting a current in the lateral direction. A basic configuration of such a semiconductor element is similar to that of a MOSFET exemplified in FIG. 3. A difference includes a configuration where the semiconductor element does not include an n+ type substrate 21 illustrated in FIG. 3 and includes a heat sink 2 c. In such a configuration, the heat sink 2 c provides a current path for conducting a source-drain current. In such a semiconductor element, a current may flow in the lateral direction. The above embodiments are applicable to an element having such a configuration.

The heat sink 2 c can be made of metal. Alternatively, the heat sink 2 c may be made of a material having a high thermal conductivity. For example, a silicon substrate itself may be utilized as a heat sink 2 c.

In examples of the above embodiments, the casing 4 and the insulating layer 2 d contacts with each other. Alternatively, the casing 4 and the insulating layer 2 d may not contact with each other. For example, the casing 4 and the insulating layer 2 d may be spaced a predetermined distance away from each other. The predetermined distances may be set so as to allow favorable heat conduction therebetween, and may be 1 μm for instance.

In the above embodiments, after the insulating layer 2 d is bonded to the heat sink 2 c, the ditch 2 f is filled with an insulating material in such a manner as exemplified in FIG. 6C, FIG. 8B or the like. Alternatively, the insulating layer 2 d may not be preliminarily formed on the heat sink 2 c, but the insulating layer 2 d may be formed at a same time when the side-wall insulating layer 2 e is formed, by applying the insulating material to a surface of the heat sink 2 c in addition to the ditch 2 f.

In second and third embodiments, an insulating material is placed in the ditch 2 f, and then, the dicing cut is performed. In such a case, a corner portion of the semiconductor chip 2, that is, an end portion of the side-wall insulating layer 2 e may become sharp. As shown in FIG. 19, the end portion of the side-wall insulating layer 2 e may be made rounded by, for example, polishing, etching (e.g., physical etching, chemical etching), or the like.

In the above embodiments, the ditch 2 f is fully filled. Alternatively, the ditch 2 f may be partially filled with an insulating member if the insulating member formed on a side wall of the ditch 2 f can have a thickness enough to provide, for example, a side-wall insulating film 2 e.

In the above embodiments, a semiconductor device mainly employs a face-down mounting structure. Alternatively, a configuration of the above embodiments is applicable to a semiconductor device that employs a face-up mounting structure. A semiconductor device with a face-up mounting structure can be manufactured by utilizing a method of the above embodiments.

While the invention has been described above with reference to various embodiments thereof, it is to be understood that the invention is not limited to the above described embodiments and construction. The invention is intended to cover various modifications and equivalent arrangements. In addition, while the various combinations and configurations described above are contemplated as embodying the invention, other combinations and configurations, including more, less or only a single element, are also contemplated as being within the scope of embodiments. 

1. A semiconductor device comprising: a casing made of metal; a board having a wiring pattern; and a semiconductor chip including: a semiconductor substrate; an element part located in the semiconductor substrate, having an element, and having first and second surface opposite to each other; an electrode part located on the first surface of the element part to provide an electrical connection to the element of the element part; a heat sink bonded to the second surface of the element part; an insulating layer located on the heat sink so that the heat sink is located between the element part and the insulating layer; and a side wall insulating layer covering all of end faces of the heat sink, wherein: the semiconductor chip is located between the casing and the board, so that the electrode part of the semiconductor chip is electrically connected with the wiring pattern of the board, and so that heat from the heat sink is radiated toward the casing via the insulating layer.
 2. The semiconductor device according to claim 1, wherein: the side wall insulating film covers all of end faces of the semiconductor chip.
 3. The semiconductor device according to claim 1, wherein: the semiconductor chip has a corner portion; and the side wall insulating film has a rounded portion that covers the corner portion of the semiconductor chip.
 4. The semiconductor device according to claim 2, wherein: the semiconductor chip has a corner portion; and the side wall insulating film has a rounded portion that covers the corner portion of the semiconductor chip. 